Interpretive Summary: Chikungunya virus was found in August 2004 to be the cause of a febrile disease epidemic in humans in a coastal island city in Kenya. This epidemic spread to Indian Ocean islands and India, where it continues and more than 1 million cases are suspected. A chikungunya fever outbreak in Italy, the first reported in a temperate country, first involved a human case who had traveled from India in June 2007 and then the involvement of 205 cases in the area during July-September 2007. Concurrently chikungunya virus was detected in local Asian tiger mosquitoes, which were first introduced into Italy in 1990 and are now widespread. The chain of chikungunya fever outbreaks from Kenya to Italy reflects a convergence of factors including: rapid international transport, previous introduction of exotic mosquito species, inadequate mosquito control, and climatic conditions. Increasingly important in vector-borne disease emergence, these factors have facilitated other recent epidemics involving imported microbes and local vectors. For high-income countries, the increasing range of vector-borne diseases suggests two major implications: First is the need to maintain vector control capabilities, and second countries should recognize that public health system weaknesses in developing countries endanger all countries. The expanding range of “tropical” infections may encourage high-income countries to perceive them as shared risks, and provide additional resources to control them at their source.

Technical Abstract:
In August 2004, Kenyan health authorities and partners identified chikungunya virus as the cause of a febrile epidemic in humans in a coastal island city. This epidemic spread to Indian Ocean islands and India, where it continues and more than 1 million cases are suspected. Rezza and colleagues describe a chikungunya fever outbreak in Italy, the first reported in a temperate country. The index case, traveling from India in June 2007, fell ill while visiting a northeastern village, and they identified 205 cases in the area during July-September, and concurrently detected chikungunya virus in local Aedes albopictus mosquitoes, which were first reported in Italy in 1990 and are now widespread. The chain of chikungunya fever outbreaks from Kenya to Italy reflects a convergence of factors including: rapid international transport, previous introduction of exotic mosquito species, inadequate mosquito control, and climatic conditions. Increasingly important in vector-borne disease emergence, these factors have facilitated other recent epidemics involving imported microbes and local vectors. For high-income countries, the increasing range of vector-borne diseases suggests two major implications: First is the need to maintain vector control capabilities, and second countries should recognize that public health system weaknesses in developing countries endanger all countries. The expanding range of “tropical” infections may encourage high-income countries to perceive them as shared risks, and provide additional resources to control them at their source.